The embodiments described herein relate generally to rotating machines and, more particularly, to methods and apparatus for assembling turbine engines.
At least some known turbine engines include a plurality of rotating turbine blades or buckets that channel high-temperature fluids, through gas turbine engines, or that channel steam through steam turbine engines. Known turbine buckets are typically coupled to a wheel portion of a rotor within the turbine engine and cooperate with the rotor to form a turbine section. Moreover, known turbine buckets are spaced circumferentially in a row extending about the rotor. Moreover, known turbine buckets are typically arranged in axially-spaced rows that are separated by a plurality of stationary nozzle segments that channel the fluid flowing through the engine towards each subsequent row of rotating buckets. Each row of segments, in conjunction with an associated row of turbine buckets, is usually referred to as a turbine stage and most known turbine engines include a plurality of turbine stages.
Moreover, at least some of the known gas turbine engines also include a plurality of rotating compressor blades that channel air through the gas turbine engine. Known rotating compressor blades are typically spaced circumferentially in axially spaced rows. Many known compressors also include a plurality of stationary nozzle segments, or stator vanes that channel air downstream towards the rotating compressor blades.
At least some known turbine buckets and/or known compressor blades each include an airfoil portion coupled to a platform portion. Platform portions of compressor blades and of turbine blades are generally circumferentially separated by a small tolerance. At least some known platforms are rectangular, and during operation, thermal expansion of the platforms reduces the small circumferential tolerances such that adjacent platforms may contact each other. Such contact forces are generally collinear, such that no net bending moment is induced to the turbine buckets and/or compressor blades, and such that a potential for overlapping or overhanging, that is, shingling of adjacent platforms is low. However, because some larger airfoils may not fit within a surface area defined by such platforms, a size of airfoils that may be used may be limited.
To accommodate larger airfoils at least some known platforms use non-rectangular geometries. However, contact of non-rectangular platforms such as trapezoidal shaped platforms induce nonlinear contact forces in the platforms, and/or induce torsional forces and/or bending moments into the turbine buckets and/or compressor blades. Over time, a likelihood or shingling of adjacent platforms is increased as compared to rectangular platforms. Such shingling may shorten a useful life of the associated turbine bucket and/or compressor blade.